The mechanisms of sensory transduction of pulmonary reactive oxygen species (ROS) by capsaicin‐sensitive vagal lung afferent fibres are unclear. To investigate the role of transient receptor potential vanilloid 1 (TRPV1) receptors and P2X purinoceptors in this sensory transduction, we recorded fibre activity (FA) from 132 fibres of this type in 132 anaesthetized and ventilated rats. Airway challenge of aerosolized H₂O₂ (0, 0.2 and 0.4%) produced a concentration‐dependant fibre stimulation. The fibre responses to 0.4% H₂O₂ were attenuated by dimethylthiourea (a hydroxyl radical (·OH) scavenger; change in fibre activity (ΔFA), −55 ± 9%) or deferoxamine (an iron‐chelator that prevents formation of ·OH; ΔFA, −59 ± 9%), were prevented by catalase (an enzyme catalysing H₂O₂; ΔFA, −96 ± 3%) and were unaffected by the vehicle for dimethylthiourea, iron‐saturated deferoxamine or heat‐inactivated catalase. The fibre responses to 0.4% H₂O₂ were attenuated by capsazepine (a TRPV1 receptor antagonist; ΔFA, −39 ± 9%) or iso‐pyridoxalphosphate‐6‐azophenyl‐2′,5′‐disulphonate (iso‐PPADS, a P2X receptor antagonist; ΔFA, −51 ± 9%), were further reduced by capsazepine and iso‐PPADS in combination (ΔFA, −70 ± 13%), and were unaltered by their vehicles. The fibre responses to cigarette smoke (20 ml), an irritant that generates ROS, were attenuated by dimethylthiourea (ΔFA, −61 ± 9%) or capsazepine and iso‐PPADS in combination (ΔFA, −67 ± 9%). These results suggest that both the TRPV1 and P2X receptors mediate the sensory transduction of ROS, especially H₂O₂ and ·OH, by capsaicin‐sensitive vagal lung afferent fibres.

Fungal allergens are associated with the development of asthma, and some have been characterized as proteases. Here, we established an animal model of allergic airway inflammation in response to continuous exposure to proteolytically active Pen c 13, a major allergen secreted by Penicillium citrinum. In functional analyses, Pen c 13 exposure led to increased airway hyperresponsiveness, significant inflammatory cell infiltration, mucus overproduction, and collagen deposition in the lung, dramatically elevated serum levels of total IgE and Pen c 13-specific IgE and IgG1, and increased production of the Th2 cytokines IL-4, IL-5, and IL-13 by splenocytes stimulated in vitro with Pen c 13. To examine the mechanisms involved in the regulation of allergenicity by Pen c 13, we performed two-dimensional fluorescence difference gel electrophoresis analysis combined with nano-LC-MS/MS, followed by bioinformatics analysis to identify potential targets that associated with allergic inflammation, which suggested that galectin-3 and laminin might be involved in novel pathogenic mechanisms. Finally, we focused on junctional proteins between cells, because, in addition to opening of the epithelial barrier by environmental proteases possibly being the initial step in the development of asthma, these proteins are also associated with actin rearrangement. Taken together, our findings indicate that Pen c 13 exposure causes junctional structure alterations and actin cytoskeletal rearrangements, resulting in increased permeability and airway structural changes. These effects probably change the lung microenvironment and foster the development of allergic sensitization.

Capsaicin-sensitive lung vagal afferents (CSLVAs) are important in detecting pulmonary reactive oxygen species (ROS). We investigated the mechanisms underlying the stimulation of CSLVAs by inhaled cigarette smoke (CS) in 216 anesthetized rats. In spontaneously breathing rats, CS evoked a CSLVA-mediated reflex bradypnea that was prevented by N-acetyl-l-cysteine (NAC; an antioxidant), HC-030031 [a transient receptor potential ankyrin 1 (TRPA1) receptor antagonist], and iso-pyridoxalphosphate-6-azophenyl-2′,5′-disulfonate (iso-PPADS; a P2X receptor antagonist). In paralyzed, artificially ventilated rats, CS evoked an increase in CSLVA fiber activity (ΔFA) that was abolished by NAC and was attenuated by HC-030031, iso-PPADS, indomethacin (Indo; a cyclooxygenase inhibitor), and a combination of apyrase and adenosine deaminase (ADA) (ATP scavengers); the response to CS was reduced to 11.7 ± 4.0%, 39.5 ± 10.0%, 52.9 ± 14.4%, 68.7 ± 10.1%, and 47.2 ± 12.9% of control, respectively. The suppressive effect on this afferent response was not improved by a combination of HC-030031 and Indo (ΔFA = 39.5 ± 10.1% of control) compared with that induced by HC-030031 alone. In contrast, the suppressive effect was enhanced by a combination of HC-030031 and apyrase+ADA (ΔFA = 5.3 ± 4.9% of control) or a combination of iso-PPADS and Indo (ΔFA = 23.3 ± 7.7% of control) compared with that induced by HC-030031 alone or iso-PPADS alone. This afferent response was not altered by the vehicles for these drugs. These results suggest that activations of TRPA1 receptors by cyclooxygenase metabolites and P2X receptors by ATP are both necessary for the ROS-mediated stimulation of CSLVA fibers by CS in rats.